The present invention relates generally to devices for testing mechanical properties of materials and more particularly to an apparatus for evaluating the deformation characteristics of test pieces placed under mechanical load.
The extent to which particular materials are deformed will logically depend upon their structural and mechanical properties. When placing cylindrical test pieces under tensile load, the test piece will become elongated and local necking-down frequently takes place. This deformation is typically evaluated at the end of the test by determining corresponding deformation coefficients.
In previously known systems for evaluating the deformation resulting from tensile load applied to test pieces, the necked-down portions of the test pieces are reviewed or studied at a point of failure when the loading forces are no longer applied. In other known devices the amount of deformation can be continuously scanned by the use of one-dimensional gauges. Motion picture cameras have also been used to record the changing shape and deformation of the test piece during the testing process. A disadvantage of the foregoing techniques and devices for evaluating deformation in test pieces is that they are limited and are incapable of taking into account all of the effects taking place in the test piece during the loading program. The known devices are particularly suited for measuring a single characteristic but cannot evaluate the total deformation characteristics of the test piece which depend upon the structural and mechanical properties of the materials. Additionally, the degree of loading in the previously known testing devices cannot be controlled (by varying the loading program) in response to shape changes or deformation taking place in the test piece. It has been found to be an advantage to be able to control the loading program of a testing device so that such loading could correspond to predetermined alternatives for the progressive structural deformation of the material being tested as well as in response to any damage of the test piece. This ability could provide significant information in analyzing the materials being tested.
It is accordingly a principal object of the present invention to provide an apparatus for measuring and evaluating deformation characteristics of mechanically deformed test pieces which overcomes the disadvantages of the known devices.
A more specific object of the present invention is to provide an apparatus of the foregoing type which includes means for visually scanning the deformation taking place in a test piece under mechanical load and evaluating such deformation based on predefined models.
A further object of the present invention is to provide an apparatus for evaluating the deformation characteristics of mechanically deformed materials which has means connected to the loading device for controlling the loading program depending upon the deformation characteristics perceived.
Other objects, features and advantages of the present invention will become more apparent from the description of the invention in connection with the accompanying drawings which will be described more fully hereinafter.